1. Field of the Invention
The present invention generally relates to sampling techniques and, more particularly, is concerned with a sample collecting apparatus particularly suited for use in the paper making industry.
2. Description of the Prior Art
A growing number of new paper making plants employ a thermo-mechanical pulping process as opposed to a chemical pulping process employed by old plants. One significant advantage of the thermo-mechanical pulping process is that it does not, to any significant degree, emit noxious odors as does the chemical pulping process.
In the thermo-mechanical pulping process, a suitable feed stock, such as wood chips, is mechanically processed into pulp fibers having the desired length. The wood chips are initially transferred into a primary refiner where they are ground into relatively long pulp fibers by grinding components having coarse teeth. The pulp fibers are next tranferred from the primary refiner to a secondary refiner where they are ground into pulp fibers of relatively short lengths by grinding components having fine teeth. After the secondary refiner, the pulp goes through a screening process wherein a screen passes pulp fibers of lengths below a maximum allowable length and rejects over-length pulp fibers. The rejected pulp fibers are transferred to a reject refiner where they are ground to reduce their lengths to below the maximum allowed.
During processing of the rejected pulp fibers in the reject refiner under atmospheric pressure and at temperatures ranging from 160.degree. to 180.degree. F., samples have to be taken periodically from a stream of ground pulp fibers falling through a chute under the influence of gravity. These samples are then taken to a laboratory where they are subjected to appropriate quality control tests.
Heretofore, in order to take a sample, a port hole in the wall of the chute has had to be unplugged and an elongated probe inserted through the hole into the pulp stream. This current procedure has certain problems. At unplugging of the port hole, frequently some of the pulp ejects from the chute through the port hole, thereby exposing the technician to hazardous contact with pulp at scalding temperatures and causing splattering and contaminating of the surrounding area with the ejected pulp.
Consequently, a need exists for improvements in the way samples are taken so as to avoid the problems of the current sampling procedure.